1. Field of the Invention
The present invention relates to a power control system and an apparatus thereof wherein a plurality of loads are independently driven.
2. Description of the Prior Arts
Usually, an inverter unit or a chopper control unit is connected for each load when a plurality of loads which can be independently driven by an inverter or a chopper are controlled.
In such system, a turn-off means is required for each electrical valve arm switched. Accordingly, it is not economical.
Usually, when a plurality of electrical valves are used in an inverter device or a chopper control device, it is not economical to provide a turn-off means for each electrical valve. Accordingly, it has been proposed to provide a common turn-off means for all electrical valves to turn them off them.
However, in the known common turn-off system, the electrical valve group is reverse-biased by the charge of a commutation capacitor whereby the line impedance of wiring etc. is affected to cause nonuniform turn-off of the electrical valves and the preciseness of the reverse-bias is disadvantageously decreased when the number of electrical valves for turn-off is increased.